1. Field of the Invention
This invention relates to a huller for the removal of the hull containing a pistachio nut particularly directed to a method and apparatus which ruptures and abrades the hull from the pistachio nut.
2. Description of the Prior Art
The methods and apparatuses currently in use for pistachio dehulling work adequately but are primarily wet processing hullers using large volumes of water.
It is noted in U.S. Pat. No. 4,034,665 by Jay J. McFarland and Bertram E. Saunders for a "Pistachio Huller" that the pistachio industry has grown commercially in the San Joaquin Valley of the State of California during recent years with substantial acreage of this delicious nut being planted. These plantings are now in production and without the cheap labor of foreign countries it is not economically feasible to hull the harvested pistachios by hand. Noted in that patent is the statement that insofar as they could determine, prior to their invention, there had never been a practical mechanical huller for pistachios. The McFarland, et al patent discloses a two stage huller, the first stage to rupture the pericarps and to remove a portion of the hull and a second stage to strip the remaining portion of the pericarp from the shells. This patent discusses one embodiment used in connection with water wherein a water nozzle provides water to moisten and soften the pericarp and to rinse the fragments of pericarp from the shell. This type of prior art huller, in application, is water assisted, as are other prior art hullers where substantial amounts of water are used. Further, the hulling of pistachio nuts is known to present unusual problems. The hulls must be promptly removed after harvest or discoloration to the pistachio shell will occur within 24 hours and damage to the nut can result if the pistachio hull is not promptly removed after harvest. The hull of the pistachio is stronger than most nuts and has a greater adherence to the shell than most nuts and it is therefore more difficult to remove.
My own U.S. Pat. No. 4,448,115 (1984) describes a method and apparatus for the dry hulling of pistachio nuts and is directed to overcome the necessity for the use of water while hulling pistachio nuts and other associated problems of the prior art, but nevertheless now has been known to suffer some disadvantages:
(a.) Pins located on the rotating means can stab the pistachio nut shell and damage the pistachio nut and nut meat. PA1 (b.) The yielding material which forms the slots tends to wear out under use and requires frequent replacement during the hulling operation. PA1 (c.) Small nuts can go through the yielding slots under compression and be lost. PA1 (d.) Frequent adjustment must be made as the yielding material wears out in order to properly process the pistachio nuts. Two separate means of adjustment were provided for this purpose. PA1 (e.) Capacity of the roller is not fully used as nuts must go through adjacent slot areas alternately - not side by side. This reduces effective capacity by one-half. PA1 (f.) There can be no assurance that suitable yielding material can be continued to be provided to meet the specification required at a reasonable price. PA1 (g.) The huller requires removal of many components to do maintanance on the machine and or replacement of the yielding material. PA1 (h.) Training is required to operate the machine to its best capacity, and must be monitored frequently to assure proper setting for correct hulling operations.